1. Field of the Invention
The present invention relates to a locking device for two, displaceable relative to each other components, in particular to components of a height-adjustable or inclination-and/or length-adjustable steering column and having arranged opposite each other, toothed racks having each tooth located alongside each other, including a clamping device which provides for movement of the two components toward each other so that teeth of the opposite toothed racks are brought into engagement with each other, and in an open position of which, the opposite toothed racks are spaced from each other and the two components can be displaced relative to each other; and at least one, displaceable against a spring biasing force, operating element provided on at least one of the opposite toothed racks for preventing tips of the teeth of the opposite toothed racks being located opposite each other during closing of the clamping device.
2. Description of the Prior Art
The use of toothed racks for locking height adjustable or inclination-and/or length-adjustable steering columns in different adjustable positions is well known. The steering columns of this type are disclosed in European Publications EP 0 836 981 B1; EP 0 440 403 B1; EP 0 755 842 B1 and German Publications DE 36 19 125 C2 and DE 195 42 472. The use of formlocking elements, in particular in form of toothed racks, permits to obtain a relatively inexpensive and reliable construction for applying necessary holding forces to a steering column in its locking condition. Nevertheless, with the construction in which toothed racks are used, at certain adjustments of two components relative to each other, problems can be encountered during regular locking of the components in their desired adjusted position. These problems appear when the tips of the teeth of two toothed racks are located directly opposite each other, in a so-called “head-to-head” position. If in this position of both components, the locking device is closed with a clamping device, the clamping device would be blocked or it could actually be closed but the tips of the teeth of the toothed racks would engage each other, and no formlocking engagement would take place. Thus, the clamping device should be open, the two components should be shifted relative to each other, whereby the tips of teeth of the two toothed racks become offset, and the clamping device should be closed again. In a worst case scenario, in case of an accident, with only seemingly closed position of the locking device, an uncontrolled relative movement between steering column components could take place, which would present a danger to a driver.
Already, different devices have been proposed for preventing the “head-to-head” position of the tips of the teeth of the toothed racks during closing of the locking device. DE 198 39 496 A1 and U.S. Pat. No. 5,787,759 disclose a device in which for preventing the “head-to-head” position of tips of mating teeth, one of the components which are provided with cooperating toothed racks, is pivotally supported. Upon displacement of the two components toward each other, the pivotally supported component pivots about an axis extending parallel to the engagement plane of the teeth and parallel to the longitudinal extent of the teeth. In a device of the German Publication DE 39 14 608 C1, there is provided a locking element displaceable in a direction toward engagement plane and pivotable about an axis extending parallel to longitudinal extent of the teeth. This device is relatively expensive and has a complicated construction, without completely eliminating a danger of the tips of the teeth being located opposite each other under any conditions.
In the locking device disclosed in German Publication DE 198 46 292, the two, located opposite each other, toothing racks are provided with magnets the magnetic forces of which provide for displacement of the adjacent free tips of the teeth away from each other. In order to provide for displacement of the two components when the tips of the teeth of both toothed racks are located opposite each other, with these magnetic devices, relatively high magnetic forces must be applied, which is associated with increased costs.
Another locking device for two, displaceable relative to each other, components provided with cooperating toothed racks is disclosed in European Publication EP 0 796 780 A2. In this device, there is provided a guide pin that is aligned parallel to the plane of the tips of the teeth and to the longitudinal extent of the teeth. The guide pin cooperates with a side guide surface provided on one of the two components. The guide surface has an inclination that corresponds somewhat to the inclination of a tooth. The guide pin is preloaded with a spring-biased clamp and occupies a position in which it extends beyond the tips of the teeth. When the toothed racks occupy a position in which the tips of the teeth are in “head-to-head” position when the two components are displaced toward each other, the guide pin extends between two teeth of the opposite toothed rack and is displaced along the guide surface, whereby the guide pin compulsory displaces sidewise the toothed rack it is associated with.
During the closing of the locking device in a position of the toothed racks in which the tips of heir respective teeth are located directly opposite each other, the toothed rack with the guide pin is displaced so far that engagement of the teeth of the two racks becomes possible. Nevertheless, even with this device, the toothed racks can occupy a position in which the guide pin is located opposite a tip of a tooth of the opposite rack, which would prevent a complete engagement of mating teeth during closing of the locking device, as the teeth of the opposite toothed racks would engage each other in the regions of their tips, preventing further displacement of the two components toward each other.
Accordingly, an object of the present invention is a locking device of the type discussed above which would insure a complete engagement of the teeth of the opposite toothed racks during closing of the locking device in any initial position of the components.